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We will present an overview of high-resolution, Navier-Stokes based
simulations of gravity and turbidity currents, with the focus on the
lock-exchange configuration. The turbidity currents considered are
driven by particles that have negligible inertia and are much smaller
than the smallest length scales of the buoyancy-induced fluid motion.
For the mathematical description of the particulate phase an Eulerian
approach is employed with a transport equation for the local particle
number density. The governing equations are integrated numerically
with finite difference and spectral/spectral-element techniques.
We will discuss differences between two- and three-dimensional gravity current dynamics. Flow features due to large, non-Boussinesq density differences will be analyzed, and differences in the dynamics of the light and heavy fronts will be discussed. In the presence of a sloping bottom the early, constant front velocity phase is seen to give rise to a second phase characterized by the dynamics of horizontal layers accelerating past each other, similar to the classical analysis by Thorpe. Some effects due to stratification of the ambient will be discussed as well. Some first results will be shown regarding the unsteady interaction of turbidity currents with submarine structures, such as a pipeline. |
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